Back in college, the wireless network didn't seem to have any protections against ARP poisoning, so I went through a short phase of messing with my roommate by

Back in college, the wireless network didn't seem to have any protections against ARP poisoning, so I went through a short phase of messing with my roommate by replacing all the images loaded by his browser with cats. Also had the classic move of replacing the desktop with a screenshot of itself and hiding the icons and taskbar. Once we got far enough into our programs we stopped messing with each other like that so as to not potentially interfere with classwork (and also the ARP poisoning stuff was probably going too far).